1. Field of the Disclosure
The present subject matter relates generally to tie rods for vehicles and more particularly to tie rods which are comprised of substantially compliant, flexible, and/or resilient material.
2. Description of Related Art
Forced steering or self-steering axle assemblies for vehicles are well known to include an elongated axle having at each end a steering knuckle. Each steering knuckle is connected to the associated end of the axle by means (typically a king pin) that allows the steering knuckle to rotate with respect to the axle. Each steering knuckle further includes a tie rod arm, with a tie rod extending between the tie rod arms, generally parallel to the associated axle in a resting (straight ahead driving) position. The tie rod is rotatably secured to the tie rod arms, commonly using ball joints, which allows the tie rod to move with the steering knuckles. The tie rod acts as a rigid linkage to cause the steering knuckles to rotate simultaneously and to the same or substantially the same extent as each other.
There are a number of disadvantages associated with known tie rods. For one, rigid tie rods can become bent and damaged if they are caused to strike an obstacle. A damaged tie rod may disrupt the alignment of the steering knuckles, which can lead to tire damage and general degradation of the performance of the vehicle.
Another disadvantage of rigid tie rods is their sub-optimal performance when one wheel (and hence the associated steering knuckle) is subjected to an abrupt input, such as driving over a bump. A rigid tie rod will absorb substantially none of the impact, thus transferring the input to the associated steering knuckle and stressing the interconnections between the tie rod, steering knuckle, and axle. Further, in this situation a rigid tie rod allows for full wheel steer, wherein an impact to one wheel causes that wheel to turn and the tie rod transfers the motion to the other wheel, such that both wheels will turn as the result of a single wheel being subjected to the impact.
Yet another disadvantage of known tie rods is that they are commonly paired with steering knuckles having relatively large and/or elongated tie rod arms, which increases the weight and cost of the axle assembly. The need to periodically lubricate the ball joints connecting the tie rod to the steering knuckles similarly increases the costs to manufacture and maintain the axle assembly.
It has been suggested to replace the rigid tie rod of a steering axle assembly with a compliant, flexible, and/or resilient tie rod. For example, the Alumi-Flex Tie Rod from Challenger Performance Products of Phoenix, Ariz. is a tubular tie rod comprised of a resilient aircraft aluminum material. The resilient material allows the Alumi-Flex Tie Rod to elastically flex upon coming into contact with an obstacle or otherwise being subjected to an impact. According to known design, the Alumi-Flex Tie Rod is rotatably secured to the tie arms of a pair of steering knuckles by ball joints, such that it moves with the steering knuckles without deforming. This adherence to conventional design yields performance results that are in line with rigid tie rods, but fails to take full advantage of the improved performance results that can be achieved by incorporating a resilient tie rod into an axle assembly as described herein.
In view of the foregoing, there is a need for a resilient tie rod that not only resists permanent deformation upon striking an object, but also provides functional advantages that are not otherwise possible with rigid tie rods. There is also a need for a tie rod that decreases the weight and cost of the associated axle assembly.